Preconditions for stable inflation in the euro zone are in place so the European Central Bank should soon start to discuss an exit from its stimulus program, Executive Board member Sabine Lautenschlaeger said on Tuesday.

A longtime critic of the ECB's ultra-easy monetary policy, she has opposed many of its easing measures in the past few years, arguing for patience with earlier moves and warning about the unintended side effects of unconventional policy measures. 

"All preconditions for a stable rise in inflation exist," Lautenschlaeger, considered one of the main hawks on the rate setting Governing Council, said in a speech. "I am thus optimistic that we can soon turn to the question of an exit."